Steel



Patented May 16, 1939 I UNITED'STATES "PATENT OFFICE STEEL Frederick M.Becket, New York, and Russell Franks, Niagara Falls, N. Y., assignors'toElec- -tro Metallurgical Company, a corporation of West Virginia NoDrawing. Application December 21, 1938,

Serial No. 246,995

3 Claims. ((71. 75-423) This invention relates to steels, and providesaffected the toughnessof the steels," or failed new and improved steelscharacterized by novel to prevent coarsening of the grain size at eleandcommercially valuable properties. This apvated temperatures, duringfabrication for in-. plication contains subject-matter in common stance,or both. The coarsening of the grain 5 with our application Serial No.87,006, filed June is considerably aggravated in a case carburizing 24,1936, process, and in such a process the addition of We have discoveredthat the addition of cocolumbium to the steel is especiallyadvantalumbium in amounts between 0.02% and 1% to geous, as illustratedby the data in Table I which so-called plain carbon and certain lowalgives the experimentally determined grain numloyed steels efiects amarked and surprising her (A. S. T. M. Specification E 19-33) of the 10improvement in the properties of such steels. cases of a series ofsteels after carburizing for One important effect of the columbiumaddition eight hours at each-of three different temperais to refine thegrain-size of the steel, and this tures. In each case, the grain size ofthe core grain refinement is retained and maintained was smaller thanthat of the case. even at elevated temperatures up to and some- Table I15 what above the critical range. Another effect, which is doubtless atleast in part a result of the grain refinement, is the improvement ofthe tensile strength of many of the steels. Further,

Composition of steel (remainder Grain No. of case after cariron)burizing 8 hours- 20 the impact strength is increased, and this im PepPep Pep Pep Pep M M M 20 provement .15 marked even at subzero temperaentcent cent cent cent 925 1, 2

0 Mn Si Cb Ni 0. c. o.

tures. There is also an increase in the resistance of the steels torusting and hot oxidation. The

machinability and the deep-drawing and cold 8- rolling characteristicsof the steels are im- 0111 0147 0 31 0.10 3145 6to9 6to9 stos 25 proved.The hardenability of the steels by heat 8- g3 g3 2-33 fizz treatment issomewhat decreased, and there is less distortion of the steel when it israpidly cooled from. elevated temperatures. The ratio $332 g i figi gfiefiegt rouihly of yield point to maximum stress is increased, 2 g otimum fg f g up a 30 the increase depending upon the columbium and r p oum 0 carbon contents of the steels: the increase is optmmm contentdepends i on the carbon greater in the steels having the lower carboncontgnt of a Steel The gram refinement and columbium contenta maximum.carbon steel reaches substan- 35 I Steels included in our invention arethose Em igi f gfif g gr g z gg 35 containing up to 1% carbon, up to 1%silicon. 1 i b te u up to 2% manganese, 0.05% to 5% nickel, 0.02% um a r9 5 e at about 018% to 0.5% columbium, remainder ir0n columbium; and a0.5% carbon steel at about Suitable amounts of columbium to be added tog moderate excess of 40 these steels according to the present inventionlumbmm above t e opum'um and below the 40 are from 0.02% to 0.5%columbium, and the most imam Specifiedabove (1%) will not ordinarilyuseful range is within the limits 0.05% to 0.25%. adrersely affect thePmperties 0f the Steel to a In general, the greater amounts of columbiumserwus extent should ordinarily be used in the steels containing Theinfluence of columbium on e t i e and 'the greater amounts of carbon,within the ranges impact Properties 0f the Steels un r o s de a- 45specified above, V tion is indicated by the data appearing inTable o oft t, valuable -ti of t II which shows the experimentally determinedcolumbium containing steels of the invention yield point in thousands ofp u d per square is that of retaining its normally fine grained inchmaximum e s in thousands of structure at elevated temperatures, whichproppounds p Square inch pe a 50 erty is attained without detrimentaliyaffecting elongation in a 2 h gage length (Eland other importantphysical properties, The xreduction in area (R. A. all on 0.505 inchpedients heretofore customarily employed to rediameter A. S. T. M.standard tensile test pieces; fine the grain size of carbon andlow-alloyed and also the Izod impact value in foot pounds steels have,in most cases, either detrimentally as determined on a standard Izodmachine with 55 an initial energy level of foot pounds and a standardspecimen one centimeter square provided with a 45 notch.

Table [1 Composition of steel (remainder iron) Tulane M El. R.A.

9' 7 Izod 9.30 g; 9, %Cb Y.P. M.s. 5 5;; mm

Qumdled in of! from800 0., draamin m M 0.

0.16 0.36 0.16 3.49 None 74 99.5 22 49 46 0.17 0.47 0.31 3.45 0.10 53102 21 30 57 0.18 0.45 0.25 3.5 0.18 56 100 27 64 52 Queaded inwaterfront 876 0., drawn in air M550 0.

0.37 0.40 0.17 3.52 None 116 129 7.5 21 23 0.34 0.35 0.13 3.45 0.084 101113 16 47 40 0.32 0.45 0.25 3.5 0.13 97 115 22 60 41 Quendled in oilfrom 860 0., drawn in air at 495 C.

0.51 0.70 0.25 3.5 None 104 7 16 3.8 0.47 0.80 0.31 3.42 0.084 191 12 378 0.51 0.75 0.25 3.5 0.18 170 183 11 38 15 0.54 0.76 0.25 3.5 0.46 170184 12 41 11 Air-cooled from 850 CW C 0.10 0.36 0.16 an None s4 77 32 e261 0.17 0.47 0.31 3.45 0. 70 82 27 50 73 0.18 0.45 0.25 3.5 0.18 65 8431 65 78 0.37 0.40 0.17 3.52 None 68 97 17 J0 29 0.34 0.35 0.13 3.460.084 72 94 25 43 37 0.32 0.45 0.25 3.5 0.13 69 94 27 54 47 0.51 0.760.25 3.5 None 94 134 2 5 3.5 0.47 0.80 0.31 3.42' 0.084 102 144 10 15 50.51 0.75 0.25 3.5 0.103 77 124 20 45 29 0.54 0.75 0.25 3.5 0.462 82 13117 36 19 sense that high chromium steels, for instance,

are oxidation resistant, the increase in resistance will be valuable inmany uses of the steels.

The articles of the invention include articles deep-drawn from the steelof the invention; articles having a core containing less than 0.5%carbon and a carburized case containing more than 0.8% carbon, and 0.02%to 0.5% columbium throughout; parts of machines and of other apparatus,required to withstand stress at moderately elevated temperatures;articles, composed of the steel of the invention, designed for use toresist impact shock at subzero temperatures; and pressure vessels,composed of the steel of the invention, designed to withstand two orthree dimensio'nal stress at subzero temperatures.

It will be appreciated that the specific examples herein are given byway of illustration, and that the invention is not limited to or by suchexamples.

We claim:

1. Steel containing carbon in an amount not exceeding 1%, manganese inan amount not exceeding 2%, silicon in an amount not exceeding 1%, 0.05%to 5% nickel, and 0.02% to 0.5% columbium, remainder iron; the columbiumacting to impart to said steel a fine-grained structure which persistsat all temperatures up to and somewhat above the critical range.

2. Steel containing carbon in an amount not exceeding 0.6%, manganese inan amount not over 2%, silicon in an amount not over 1%, 0.05% to 5%nickel, and 0.05% to 0.25% columbium, remainder iron; the columbiumacting to impart to said steel 8. fine-grained structure which persistsat all temperatures up to and somewhat above the critical range.

3. Case carburized article having a core containlng less than 0.5%carbon and e. carburized case containing more than 0.8% carbon, the coreand case being composed of steel containing, aside from carbon,manganese in an amount not over 2%, silicon in an amount not exceeding1%, 0.05% to 5% nickel, and 0.05% to 0.25% columbium, remainder iron;the colwnbium acting to impart to said carburized article a fine-grainedstructure, increased ductility, and increased impact strength.

